This invention relates to a semiconductor device and, more particularly, to a semiconductor device having outer leads which extend in a canti-levered manner from a mold-resin and a manufacturing method therefor.
FIG. 8 is a sectional view illustrating a conventional process of lead-forming outer leads of a semiconductor device and FIG. 9 is a perspective view of a conventional semiconductor device after the lead-forming. In FIGS. 8 and 9, a conventional semiconductor device 1 comprises a mold resin 1a and a number of outer leads 2 which are curved by lead-forming and which extend in a canti-levered manner from the mold resin 1a and have free ends 2a. To manufacture this semiconductor device 1, a semiconductor device which is encapsulated in a resin 1a and which is separated from the lead frame (not shown) is prepared. As generally known, the semiconductor device 1 in this state has a number of outer leads 2 which extend in a straight canti-levered manner from the mold resin 1a. As illustrated in FIG. 8, when this semiconductor device 1 is clamped between an upper die 3a and a lower die 3b of lead-forming dies 3, the upper die 3a and the lower die 3b act only on the outer leads 2 to bend and form them according to the shape of the lead-forming dies 3 as illustrated in FIG. 8. After the lead-forming, the semiconductor device 1 with the formed outer leads 2 is taken out from the lead-forming dies 3.
During storage, carrying, and handling of the semiconductor device 1, various external forces are exerted to the outer leads 2 and the outer leads 2 are often undesirably bent. In particular, recent semiconductor devices of a multiple-lead type or a thin type have a number of outer leads which are very narrow and thin. For example, copper leads in a semiconductor device manufactured by the TAB (Tape Automated Bonding) technique may have a thickness of about 35 .mu.m. In these semiconductor devices, deformations of the outer leads 2 occur very easily, and as a result, the free ends 2a of the outer leads 2 are moved up and down from each original position 6 as illustrated in FIG. 9. Further the free end 2a of the outer lead 2 is sometimes shifted horizontally or it may be shifted both horizontally and vertically.
If there are defomations of the outer leads 2, the semiconductor device 1 cannot properly be mounted and soldered on a circuit board (not shown). That is, the free end 2a of the outer lead 2 of the semiconductor device 1 cannot be exactly set on a land (or a terminal) (See FIG. 7) of the circuit board, it moves often off of the land horizontally or it rises from the land undesirably.
Solder is usually provided by printing a solder cream through an opening of a mask (not shown) in which only the land is exposed. However, in the semiconductor device 1 where the width of the outer lead 2 or the pitch of the outer leads 2 is small, the above method cannot be applied because, if the width of the outer lead 2 is very small, the opening of the mask is also very small and the solder cream cannot be adequately supplied through the opening. Therefore, in the semiconductor device 1, solder is provided by solder plating. In this solder plating method, a soldering activator such as soldering flux is printed to the solder plating surface to remove an oxide film and improve the solderability which is reduced by for example, oxidation.